Manufacturing method of highly heat-resistant sound absorbing and insulating materials

ABSTRACT

The present invention relates to a method for manufacturing a substantially improved heat-resistant sound absorbing and insulating material. method includes: beating and mixing a fiber material comprising a heat-resistant fiber; forming a web from the beaten and mixed fiber material; stacking the formed web; forming a nonwoven fabric by needle punching as moving a needle up and down through the stacked web; forming a binder-impregnated nonwoven fabric by immersing the nonwoven fabric in a binder solution; and removing a solvent from the binder-impregnated nonwoven fabric. 
     The substantially improved heat-resistant sound absorbing and insulating material manufactured by the method according to the present invention may be installed on a location closest to the noise source of an engine or an exhaust system to reduce radiated noise from the engine or the exhaust system, thereby improving quietness inside a vehicle, and may be applied to a location adjacent to a metal part which is at a temperature of 200° C. or greater to exert heat-insulating function, thereby protecting nearby plastic and rubber parts.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of International Application No.: PCT/KR2013/010027 filed Nov. 6, 2013, which also claims the benefit of Korean Patent Application No. 10-2012-0124945, filed on Nov. 6, 2012, the entire contents of both applications are incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to a method for manufacturing a substantially improved heat-resistant sound absorbing and insulating material. Particularly, the method for manufacturing the substantially improved heat-resistant sound absorbing and insulating material may not change in shape even under a high-temperature environment of about 200° C. or greater and satisfy UL 94V-0 flame retardancy. The method may include a beating and mixing step, a web forming step, a web stacking step, a needle punching step, a binder impregnating step and a solvent recovering step.

BACKGROUND

Various noises are generated while driving a vehicle. The vehicle noise may be mainly generated from an engine or an exhaust system and may be transferred to the inside of a vehicle by air. A sound absorbing and insulating material has been used to reduce the noise generated from the engine and the exhaust system from being transferred to the inside of the vehicle. For example, an insulation dash, a dash isolation pad, and the like have been used to block the noise radiating from the engine from being transferred to the inside of the vehicle and a tunnel pad, a floor carpet, and the like have been used to block the noise generated from the exhaust system and the floor from being transferred to the inside of the vehicle.

In the related arts, as sound absorbing materials for a vehicle, Korean Patent Publication No. 2004-0013840 discloses a 20-mm thick sound absorbing and insulating material having a PET fiber layer in which a synthetic resin film layer having a thickness of 40-100 μm in the lengthwise direction is inserted, and Korean Patent Publication No. 2002-0089277 discloses a process for preparing a sound absorbing insulation material of a nonwoven fabric form by cutting and beating a polyester fiber and an acrylic fiber, mixing with a low-melting-point polyester fiber at a specific ratio, and molding and heating the same. And, Korean Patent Publication No. 2006-0043576 discloses a method of coating at least one of a top layer and a bottom layer of a polyester (PET) felt with a resin, using a mixture fiber of a low-melting-point fiber (LMF) and a regular fiber.

However, the sound absorbing and insulating materials for vehicles reported thus far have been limited in that weight may be inevitably increased to reduce radiated noise from the engine or the exhaust system and the efficiency of reducing noise inside the vehicle may be low when considering the weight increase. In order to overcome this limitation, it may be necessary to install the sound absorbing and insulating material on a location closest to the engine or the exhaust system. To install the sound absorbing and insulating material on the location closest to the engine or the exhaust system, shape change should not occur even under a high-temperature environment of about 200° C. or greater and flame retardancy should be ensured. For this reason, the currently used sound absorbing and insulating materials for vehicles have not been used for such applications.

The description provided above as a related art of the present invention is just merely for helping understanding of the background of the present invention and should not be construed as being included in the related art known by those skilled in the art.

SUMMARY

In preferred aspects, the present invention provides a method for manufacturing a substantially improved heat-resistant sound absorbing and insulating material, and the method may not change in shape even under a high-temperature environment of 200° C. or greater, at a location closest to the noise source of an engine or an exhaust system of a vehicle, and satisfy UL 94V-0 flame retardancy.

The present invention further provides a method for manufacturing a substantially improved heat-resistant sound absorbing and insulating material which is applied to a location adjacent to a metal part which is at a temperature of about 200° C. or greater to protect nearby plastic and rubber parts.

The present invention also provides a method for effectively manufacturing a new-concept substantially improved heat-resistant sound absorbing and insulating material which can be molded based on the three-dimensional shape of a device, such as a noise generating device.

In one aspect, the present invention provides a method for manufacturing a heat-resistant sound absorbing and insulating material. The method may include: beating and mixing a fiber material containing a heat-resistant fiber; forming a web from the beaten and mixed fiber material; stacking the formed web; forming a nonwoven fabric by needle punching as moving a needle up and down through the stacked web; forming a binder-impregnated nonwoven fabric by immersing the nonwoven fabric in a binder solution; and removing a solvent from the binder-impregnated nonwoven fabric, thereby obtaining a substantially improved heat-resistant sound absorbing and insulating material.

In another aspect, the present invention provides a method for manufacturing a heat-resistant sound absorbing and insulating material. The method may include: beating and mixing a fiber material containing: a heat-resistant fiber; forming a web from the beaten and mixed fiber material; stacking the formed web forming a nonwoven fabric by needle punching as moving a needle up and down through the stacked web; forming a binder-impregnated nonwoven fabric by immersing the nonwoven fabric in a binder solution; removing a solvent from the binder-impregnated nonwoven fabric; and shaping the dried nonwoven fabric into a sound absorbing and insulating material having a desired shape.

In an exemplary embodiment of the present invention, the beating and mixing the fiber material may include: beating a fiber material having a limiting oxygen index (LOI) of about 25% or greater and a heat resistance temperature of about 200° C. or greater, having about 1-10 crimps/cm and having a diameter of about 1-33 μm and a length of about 20-100 mm, mixing one or more fiber material having a limiting oxygen index (LOI) of about 25% or greater and a heat resistance temperature of about 200° C. or greater, having about 1-10 crimps/cm and having a diameter about of 1-33 μm and a length of about 20-100 mm, or performing beating and mixing under the above-described conditions.

The term “limiting oxygen index (LOI)”, as used herein, indicates the minimum concentration of oxygen, expressed as a percentage, that will support combustion of a polymer or material. The LOI may be typically measured by passing a mixture of oxygen and nitrogen over a burning specimen of the polymer or material, and reducing the oxygen level until a critical level is reached. The LOI values for different polymers or materials may be readily determined by such a procedure including standardized tests, such as the ISO 4589 and ASTM D2863.

In another exemplary embodiment of the present invention, the fiber material may include one or more selected from the group consisting of an aramid fiber, a polyphenylene sulfide (PPS) fiber, an oxidized polyacrylonitrile (oxi-PAN) fiber, a polyimide (PI) fiber, a polybenzimidazole (PBI) fiber, a polybenzoxazole (PBO) fiber, a polytetrafluoroethylene (PTFE) fiber, a polyketone (PK) fiber, a metallic fiber, a carbon fiber, a glass fiber, a basalt fiber, a silica fiber and a ceramic fiber.

In an exemplary embodiment of the present invention, the web may be formed by placing the fiber material beaten and mixed on a swift having workers on both sides and a cylinder of a carding machine as a fancy may rotate at high speed and the fiber may be combed to form a continuous web in the form of a thin sheet and may be performed by carding method.

In an exemplary embodiment of the present invention, the formed web may be stacked with each other by overlapping on a conveyor belt to form a stacked web and may be performed at a rate of about 10 m/min or lower using a horizontal wrapper in order to prevent scattering of the web due to air resistance and breaking of the web on the conveyor belt.

In an exemplary embodiment of the present invention, the stacked web formed in the web stacking step may be bound to each other by needle punching, in which a needle may be move up and down through the stacked web, and may be performed by one or more selected from the group consisting of single down needle punching, single up needle punching, double down needle punching and double up needle punching. In addition, in another exemplary embodiment of the present invention, the needle punching may include forming a nonwoven fabric with a needle stroke of about 30-350 times/m². Still further, in another exemplary embodiment of the present invention, by the needle punching, a nonwoven fabric may be formed to have a single layer thickness of about 3-20 mm and a density of about 100-2000 g/m².

In an exemplary embodiment of the present invention, the nonwoven fabric formed by the needle punching may be immersed in a binder solution. In particular, the binder solution may be a thermosetting binder resin which may have a heat resistance temperature of about 200° C. or greater may be dispersed in an organic solvent at a concentration of 5-70 wt %, based on the total weight of the binder solution.

In another exemplary embodiment of the present invention, the nonwoven fabric immersed into and impregnated with the binder solution may be further at a pressure of about 1-20 kgf/cm² to form a binder-impregnated nonwoven fabric having a density of about 1,000-3,000 g/m².

Alternatively, an amount of about 20-80 parts by weight of a thermosetting binder resin may be impregnated in an amount of about 20-80 parts by weight of the nonwoven fabric, based on 100 parts of the combined weights thereof.

In another exemplary embodiment of the present invention, the binder solution may include an amount of about 5-70 wt % of a binder resin, an amount of about 0.1-10 wt % of a curing agent, an amount of about 0.01-5 wt % of a catalyst, an amount of about 1-40 wt % of an additive and a solvent as the balance, based on the total weight of the binder solution.

In another exemplary embodiment of the present invention, the binder resin may be an epoxy resin. The epoxy resin may be, but not limited to, one or more selected from the group consisting of bisphenol A diglycidyl ether, bisphenol B diglycidyl ether, bisphenol AD diglycidyl ether, bisphenol F diglycidyl ether, bisphenol S diglycidyl ether, polyoxypropylene diglycidyl ether, bisphenol A diglycidyl ether polymer, phosphazene diglycidyl ether, bisphenol A novolac epoxy, phenol novolac epoxy resin, and o-cresol novolac epoxy resin.

The organic solvent may be, but not limited to, one or more selected from the group consisting of methyl ethyl ketone (MEK) and dimethyl carbonate (DMC).

In an exemplary embodiment of the present invention, the solvent may be removed by using a drying oven at a temperature of about 70-200° C. for about 1-10 minutes. In particular, when only the thermosetting binder resin is present in the nonwoven fabric by evaporating the organic solvent from the binder-impregnated nonwoven fabric formed, a thermosetting felt may be formed.

In another exemplary embodiment of the present invention, the nonwoven fabric after removing solvent may contain an amount of about 1-300 parts by weight of a binder based on 100 parts by weight of the nonwoven fabric.

In an exemplary embodiment of the present invention, the molding may be performed at a temperature of about 150-300° C.

In another aspect, the present invention provides a method for reducing noise of a noise generating device, including: i) identifying the three-dimensional shape of a noise generating device; ii) manufacturing and molding a sound absorbing and insulating material so as to correspond partially or entirely to the three-dimensional shape of the device; and iii) bringing the sound absorbing and insulating material adjacent to the noise generating device.

The term “shape” of the device, as used herein, means a distinctive form which is made or molded suitably by a suitable method used in the related arts without limitation. The shape may not be particularly limited, but the shape of the device may be formed at least a portion or entirely based on the design, without limitation. For example, the three-dimensional shape of a noise generation device of a vehicle may be molded or casted, without limited suitably by any methods generally used in the art, to provide a shape of the sound-absorbing molded material, thereby being used and attached at adjacent to the noise generation device.

In an exemplary embodiment of the present invention, the device may be, but not limited to, a motor, an engine or an exhaust system.

In an exemplary embodiment of the present invention, said bringing the sound absorbing and insulating material adjacent to the noise generating device may include closely attaching the sound absorbing and insulating material to the noise generating device, installing the sound absorbing and insulating material to be spaced apart from the noise generating device or molding the sound absorbing and insulating material as a part of the noise generating device.

In the heat-resistant sound absorbing and insulating material manufactured by exemplary methods according to the present invention, the binder impregnated into the nonwoven fabric having irregular vent holes or microcavities with a complicated three-dimensional labyrinth structure may be cured while maintaining the three-dimensional structure inside the nonwoven fabric without blocking the vent holes. Therefore, the physical properties of the nonwoven fabric including sound-absorbing property performance may be substantially improved and molding into a desired shape may be possible during the curing of the binder.

Further provided is a vehicle part, that may comprise the heat-resistant sound absorbing and insulating material manufactured by the method as described herein.

Also, since substantially improved heat-resistant sound absorbing and insulating material manufactured by the method according to the present invention wherein the binder is impregnated in the nonwoven fabric formed of the heat-resistant fiber may provide superior flame retardancy, heat resistance and heat-insulating property in addition to sound-absorbing performance, the sound absorbing and insulating material may not be deformed or denatured when applied to a noise generating device operating at temperatures of about 200° C. or greater.

In addition, the method for manufacturing a heat-resistant sound absorbing and insulating material according to exemplary embodiments of the present invention provides an effect of simplifying the manufacturing process, because the thermosetting resin may be used as the binder for molding into a desired shape while the thermosetting resin is cured.

Furthermore, the method for molding a heat-resistant sound absorbing and insulating material according to exemplary embodiments of the present invention provides a substantially improved heat-resistant sound absorbing and insulating material which may be installed on a location closest to a noise source of an engine or an exhaust system and reduces noise radiating from the engine or the exhaust system.

In addition, the method for manufacturing a substantially improved heat-resistant sound absorbing and insulating material according to exemplary embodiments of the present invention provides a sound absorbing and insulating material which may be applied to a location adjacent to a metal part which is at a temperature of about 200° C. or greater to protect nearby plastic and rubber parts.

Accordingly, the sound absorbing and insulating material manufactured by the method of the present invention may be useful for applications that may require arresting, absorbing or insulating of sound, including electric appliances such as air conditioner, refrigerator, washing machine, lawn mower, and the like, transportation such as vehicle, ship, airplane, and the like and construction materials such as wall material, flooring material and the like. In particular, the sound absorbing and insulating material manufactured by the methods according to exemplary embodiments of the present invention may be useful for a noise generating device maintained at high temperatures of about 200° C. or greater. Further, when the sound absorbing and insulating material manufactured by the method according to exemplary embodiments of the present invention may be used in a vehicle, it may be closely attached to a noise generating device of vehicle parts, such as engine, exhaust system, the like, may be installed to be spaced apart from the noise generating device or may be molded as at least a portion or an entire portion of the noise generating device.

Other aspects of the invention are disclosed infra.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawing.

FIG. 1 shows a flow chart describing an exemplary method for manufacturing a heat-resistant sound absorbing and insulating material according to an exemplary embodiment of the present invention.

FIGS. 2A-2C show electron microscopic images (×300) of exemplary nonwoven fabrics before and after impregnation of a binder. FIG. 2A is an image of a nonwoven fabric prepared by needle punching. FIG. 2B and FIG. 2C show images of exemplary binder-impregnated nonwoven fabrics. FIG. 2B is an image of an exemplary binder-impregnated nonwoven fabric in which an amount of about 20 parts by weight of a binder is impregnated in an amount of about 80 parts by weight of a nonwoven fabric, and FIG. 2C is an image of an exemplary binder-impregnated nonwoven fabric in which an amount of about 50 parts by weight of a binder is impregnated in an amount of about 50 parts by weight of a nonwoven fabric.

FIG. 3 shows an exemplary heat-resistant sound absorbing and insulating material manufactured by an exemplary method for manufacturing a heat-resistant sound absorbing and insulating material according to an exemplary embodiment of the present invention and an existing aluminum heat protector.

FIG. 4 shows an exemplary heat-resistant sound absorbing and insulating material manufactured by an exemplary method for manufacturing a heat-resistant sound absorbing and insulating material according to an exemplary embodiment of the present invention and a conventional aluminum heat protector, which are respectively installed to reduce radiated noise from an exemplary exhaust system.

FIGS. 5A-5B schematically show examples wherein an exemplary sound absorbing and insulating material is molded and applied to an exemplary noise generating device of a vehicle. FIG. 5A shows an image of an exemplary sound absorbing and insulating material molded for use in a vehicle engine, and FIG. 5B shows an image of an exemplary sound absorbing and insulating material installed on a part of a vehicle engine.

FIGS. 6A-B schematically show examples wherein an exemplary sound absorbing and insulating material is applied to an exemplary noise generating device of a vehicle to be spaced apart from the noise generating device. FIG. 6A shows an image of an exemplary sound absorbing and insulating material molded for use in a lower part of a vehicle, and FIG. 6B shows an image of an exemplary sound absorbing and insulating material installed on a lower part of a vehicle.

FIG. 7 compares the sound-absorbing performance of an exemplary sound absorbing and insulating material depending on the density of a nonwoven fabric.

FIG. 8 compares the heat-insulating performance of an exemplary heat-resistant sound absorbing and insulating material manufactured according to an exemplary method for manufacturing a heat-resistant sound absorbing and insulating material according to an exemplary embodiment of the present invention with that of an existing aluminum heat-insulating plate.

DETAILED DESCRIPTION

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items.

Unless specifically stated or obvious from context, as used herein, the term “about” is understood as within a range of normal tolerance in the art, for example within 2 standard deviations of the mean. “About” can be understood as within 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, 0.5%, 0.1%, 0.05%, or 0.01% of the stated value. Unless otherwise clear from the context, all numerical values provided herein are modified by the term “about.”

It is understood that the term “vehicle” or “vehicular” or other similar term as used herein is inclusive of motor vehicles in general such as passenger automobiles including sports utility vehicles (SUV), buses, trucks, various commercial vehicles, watercraft including a variety of boats and ships, aircraft, and the like, and includes hybrid vehicles, electric vehicles, plug-in hybrid electric vehicles, hydrogen-powered vehicles and other alternative fuel vehicles (e.g. fuels derived from resources other than petroleum). As referred to herein, a hybrid vehicle is a vehicle that has two or more sources of power, for example both gasoline-powered and electric-powered vehicles.

Hereinafter, various exemplary embodiments of the present invention will be described in detail. However, they are only intended to describe the present invention in detail such that those of ordinary skill in the art to which the present invention belongs can easily carry out the invention and the technical idea and scope of the present invention are not limited by them.

The present invention provides a method for manufacturing a heat-resistant sound absorbing and insulating material that may include: beating and mixing a fiber material comprising a heat-resistant fiber having a limiting oxygen index (LOI) of about 25% or greater and a heat resistance temperature of about 200° C. or greater; forming the fiber material beaten and mixed in the beating and mixing step into a continuous web in the form of a thin sheet; stacking the formed web; forming a stacked web by overlapping and stacking the web formed in the web forming step with each other; forming a nonwoven fabric by needle punching as binding the stacked web with each other, for example, by moving a needle up and down through the stacked web; forming a binder-impregnated nonwoven fabric by immersing the nonwoven fabric in a binder solution; and forming a thermosetting felt for use as a sound absorbing and insulating material by removing the solvent from the binder-impregnated nonwoven fabric such that only the thermosetting binder resin may remain. In particular, the thermosetting binder resin may include a heat resistance temperature of about 200° C. or greater that may be dispersed in an organic solvent

The method for manufacturing a heat-resistant sound absorbing and insulating material may further include, after removing the solvent, the dried nonwoven fabric may be shaped into a desired shape by molding at a temperature of about 150-300° C.

A sound absorbing and insulating material manufactured by exemplary methods according to the present invention may have a binder distributed uniformly on the entire fiber yarn of the nonwoven fabric containing a heat-resistant fiber and may have fine vent holes or microcavities formed as compared to before the impregnation of the binder. Accordingly, superior sound-absorbing performance, flame retardancy, heat resistance and heat-insulating property may be obtained and the sound-absorbing material may be molded into a desired three-dimensional shape due to the binder impregnated in the same layer as the nonwoven.

The term “microcavity” or “microcavities”, as used herein, may be a feature formed inside a nonwoven fabric layer and formed by fibers which may be regularly or irregularly arranged inside the nonwoven fabric layer. Further, the microcavities may be formed by any kinds of material inside the nonwoven fabric, whether inherently existed or subsequently added. The microcavities also may be formed by a binder, a resin additive, or the like, without limitation. The microcavities may include any kinds of internal space or vacancy. The microcavities may be open to outside of the nonwoven fabric or be connected therebetween inside the nonwoven fabric layer. The microcavity may be, but not limited to a pore, a hole, a labyrinth, a channel, or the like. Size dimension of the microcavity may vary from several nanometer scale to hundreds micrometer scale, without limitation. In particular, the microcavity may provide a resonance path of sound or noise, and further provide a sound absorbing property. The resonance path of a sound in the microcavities may not be limited to a specific frequency of sound.

As shown in FIG. 1, the method for manufacturing a heat-resistant sound absorbing and insulating material according to an exemplary embodiment of the present invention includes a beating and mixing step S101, a web forming step S103, a web stacking step S105, a needle punching step S107, a binder impregnating step S109 and a solvent recovering step S111.

The method for manufacturing a substantially improved heat-resistant sound absorbing and insulating material according to the present invention will be described in detail referring to the flow chart of FIG. 1.

The beating and mixing step S101 may include beating a fiber material having a limiting oxygen index (LOI) of about 25% or greater and a heat resistance temperature of about 200° C. or greater, having about 1-10 crimps/cm and having a diameter of about 1-33 μm and a length of about 20-100 mm, mixing one or more fiber material having a limiting oxygen index (LOI) of about 25% or greater and a heat resistance temperature of about 200° C. or greater, having about 1-10 crimps/cm and having a diameter of about 1-33 μm and a length of about 20-100 mm, or performing beating and mixing under the above-described conditions. For example, air blowing may be conducted to uniformly disperse the fiber.

The fiber material used in the beating and mixing step S101 of the present invention may be a base material of the heat-resistant sound absorbing and insulating material and serve to reduce noise transferred to the inside of a vehicle by absorbing the noise radiating from an exemplary noise generating vehicle part, such as an engine or an exhaust system.

In the present invention, a heat-resistant fiber having a limiting oxygen index (LOI) of about 25% or greater and a heat resistance temperature of about 150° C. or greater may be used as the fiber material. The heat-resistant fiber may be any one that has superior durability so as to endure high-temperature and ultra-high-temperature conditions. In particular, a heat-resistant fiber having a limiting oxygen index (LOI) of about 25-80% and a heat resistance temperature of about 150-3000° C. may be used. Further, in particular, a heat-resistant fiber having a limiting oxygen index (LOI) of about 25-70% and a heat resistance temperature of about 200-1000° C. may be used. And, the heat-resistant fiber may have a fineness of about 1-15 denier, or particularly of about 1-6 denier, and a yarn length of about 20-100 mm, or particularly of about 40-80 mm. When the yarn length is less than the predetermined range, for example, less than about 20 mm, the binding strength of the nonwoven fabric may be reduced because of difficulty in yarn bridging during needle punching. And, when the yarn length is greater than the predetermined range, for example, greater than about 100 mm, the yarn may not be transferred as desired during carding although the nonwoven fabric may have good binding strength.

As the heat-resistant fiber, one known as ‘superfiber’ generally known in the related art may be used. Particularly, the superfiber may be one or more selected from the group consisting of an aramid fiber, a polyphenylene sulfide (PPS) fiber, an oxidized polyacrylonitrile (oxi-PAN) fiber, a polyimide (PI) fiber, a polybenzimidazole (PBI) fiber, a polybenzoxazole (PBO) fiber, a polytetrafluoroethylene (PTFE) fiber, a polyketone (PK) fiber, a metallic fiber, a carbon fiber, a glass fiber, a basalt fiber, a silica fiber and a ceramic fiber. Among those, an aramid fiber may be used as the heat-resistant fiber in the present invention. For example, a meta-aramid fiber, a para-aramid fiber or a mixture thereof may be used as the heat-resistant fiber in the present invention.

The aramid fiber, as used herein, may be an aromatic polyamide fiber in which aromatic rings such as benzene ring are bonded with each other by amide groups. The aromatic polyamide fiber is typically called as ‘aramid’ and distinguished from an aliphatic polyamide, for example, nylon. The aramid fiber may be prepared by spinning of aromatic polyamide and classified as meta-aramid (m-aramid, Chemical Formula 1) and para-aramid (p-aramid, Chemical Formula 2) depending on the location of the amide bonds on the aromatic ring.

The meta-aramid (m-aramid) represented by Chemical Formula 1 may be prepared by dry spinning after dissolving isophthaloyl chloride and m-phenylenediamine in a dimethylacetamide (DMAc) solvent. The meta-aramid has a relatively high tensile elongation at break in a range of about 22-40% due to the uneven polymer structure. The meta-aramid may be dyed and may be easily prepared into fibers. It is appreciated that Nomex™ (DuPont, USA), Conex™ (Teijin, Japan) and the like may provide a range of options for the m-aramid, but the examples are not limited thereto.

The para-aramid (p-aramid) represented by Chemical Formula 2 may be prepared by wet spinning after dissolving terephthaloyl chloride and p-phenylenediamine in an N-methylpyrrolidone (NMP) solvent. The para-aramid may have high strength due to its highly oriented linear molecular structure, about 3-7 times greater compared to meta-aramid. For this reason, the p-aramid may be used for reinforcement or protection materials. Further, the p-aramid may have strong chemical resistance, reduced thermal shrinkage, superior dimensional stability and high tear strength as well as flame resistance and self-extinguishing property. It is appreciated that Kevlar™ (DuPont, USA), Twaron™ (Teijin, Japan) and Technora™ (Teijin, Japan) may provide a range of options for the p-aramid, but the examples are not limited thereto.

The aramid may be provided in the form of filament, staple, yarn and the like and may be used for reinforcing materials (e.g., transformer, motor, and the like), insulating materials (e.g., insulating paper, insulating tape, and the like), heat-resistant fibers (e.g., fireproof clothing, fireproof gloves, and the like), high-temperature filters, or the like.

Although a heat-resistant fiber is used as the fiber material for preparing the sound absorbing and insulating material in the present invention, another fiber may be further included in addition to the yarn of the heat-resistant fiber for the purpose of cost reduction, weight decrease, functionality, and the like. In other words, although the sound absorbing and insulating material of the present invention may be prepared from a heat-resistant fiber as a yarn, it may not be limited to a sound absorbing and insulating material consisting only of a heat-resistant fiber. The heat-resistant fiber yarn included in the sound absorbing and insulating material of the present invention may be included in an amount of 30-100 wt %, or particularly of about 60-100 wt %, based on the total weight of the fiber material.

In the web forming step S103, the fiber material beaten and mixed in the beating and mixing step S101 may be placed on a swift having workers on both sides and a cylinder of a carding machine as a fancy may rotate at high speed and the fiber may be combed to form a continuous web in the form of a thin sheet. In particular, carding method may be performed and provide bulkiness to the formed web and minimizes weight scattering by maximizing fiber modification efficiency.

In the web stacking step S105, the web formed in the web forming step S103 may be stacked with each other by overlapping on a conveyor belt to form a stacked web and may be performed at a rate of about 10 m/min or less using a horizontal wrapper in order to prevent scattering of the web due to air resistance and breaking of the web on the conveyor belt.

The needle punching step S107 is a step wherein the stacked web formed in the web stacking step S105 may be bound to each other by moving a needle up and down through the stacked web in a direction perpendicular or oblique or both to the surface of the stacked web and may be performed by one or more selected from the group consisting of single down needle punching, single up needle punching, double down needle punching and double up needle punching. In this step, the binding strength of the nonwoven fabric may be increased as the stacked web arranged in a horizontal direction is partly arranged vertically.

The nonwoven fabric formed in the needle punching step S107 may have a single layer thickness of about 3-20 mm and a density of about 100-2000 g/m². Sound-absorbing performance may vary depending on the thickness and density of the nonwoven fabric. It is expected that the sound-absorbing performance may be increased with increasing thickness and density of the nonwoven fabric. When considering the industrial application, and the like of the sound absorbing and insulating material of the present invention, the nonwoven fabric may have a thickness of about 3-20 mm. When the thickness of the nonwoven fabric is less than about 3 mm, the durability and moldability of the sound absorbing and insulating material may be unsatisfactory. And, when the thickness is greater than about 20 mm, productivity may decrease and production cost may increase during manufacturing and processing the nonwoven fabric. In addition, the density of the nonwoven fabric may be about 100-2000 g/m², about 200-1200 g/m², or particularly about 300-800 g/m², in the aspects of performance and cost.

The aramid nonwoven fabric may be formed by stacking a web of about 30-100 g/m² which may be formed by carding method about 2- to 12-fold and continuously performing up-down preneedling, down-up needling and up-down needling, thereby forming physical bridges and providing the desired thickness, binding strength and other desired physical properties. The needle used to perform the needling may be a barb-type needle, having a working blade of about 0.5-3 mm and a needle length (crank outside-to-point distance) of about 70-120 mm. For example, the needle stroke may be about 30-350 times/m².

Particularly, the fineness of the yarn for the nonwoven fabric may be about 1.5-8.0 denier, the thickness of the pile layer may be about 6-13 mm, the needle stroke may be about 120-250 times/m², and the density of the nonwoven fabric may be about 300-800 g/m².

The binder impregnating step S109 includes immersing the nonwoven fabric formed in the needle punching step S107 in a binder solution wherein a thermosetting binder resin having a heat resistance temperature of about 200° C. or greater may be dispersed in an organic solvent at a concentration of 5-70 wt %, based on the total weight of the thermosetting binder resin. The binder impregnating step S109 may further include, if necessary, compressing the binder-impregnated nonwoven fabric. The compression may be performed to control the content of the thermosetting binder resin in the nonwoven fabric. Particularly, the compression may be performed at a pressure of about 1-20 kgf/cm² using a commonly used compression roller in order to form a binder-impregnated nonwoven fabric having a density of about 1,000-3,000 g/m². Alternatively, the compression may be performed using a compression roller, e.g., a mangle roller, at a pressure of about 5-15 kgf/cm² to form a binder-impregnated nonwoven fabric having a density of about 1,000-2,000 g/m².

The binder impregnating step S109 includes impregnating an amount of about 20-80 parts by weight of a thermosetting binder resin in an amount of about 20-80 parts by weight of the nonwoven fabric, based on 100 parts of total weight.

The binder impregnating step S109 may not only improve the sound-absorbing and insulating performance but also mold the sound absorbing material into a desired shape.

The nonwoven fabric has a structure in which fibers are randomly arranged in three dimensions, although there may be some variations depending on the manufacturing method. Therefore, the inside of the nonwoven fabric may have a very complicated, three-dimensionally interconnected labyrinth structure, which is formed by regularly or irregularly arranged fibers, may be, rather than bundles of independent capillary tubes. Thus, the nonwoven fabric formed in the needle punching step S107 may contain irregular vent holes or microcavities formed as the yarns containing the heat-resistant fiber loosely cross one another.

In the present invention, by performing the binder impregnating step S109 of immersing the nonwoven fabric in the binder solution, the binder may be distributed uniformly on the entire fiber yarn of the nonwoven fabric containing the heat-resistant fiber and, as a result, the vent holes or microcavities with fine size as compared to before the impregnation of the binder may be formed while substantially maintaining the intrinsic (original) three-dimensional pore structure of the nonwoven fabric. The formation of fine vent holes or microcavities in the internal structure of the nonwoven fabric provides an extended resonance path of noise, and thus, provides improved sound-absorbing performance. When the binder resin forms a three-dimensional network structure as it is cured, the sound-absorbing performance can be further improved by forming more and finer vent holes or microcavities inside the nonwoven fabric. Accordingly, since the nonwoven fabric may maintain the intrinsic (original) three-dimensional shape as the binder is uniformly impregnated into the nonwoven fabric, and additionally, since more fine vent holes or microcavities may be formed as the binder is cured, the sound absorbing and insulating material of the present invention may have remarkably improved sound-absorbing performance due to the maximized noise absorption through the increased resonance of noise in the nonwoven fabric.

In the binder-impregnated nonwoven fabric that has passed through the binder impregnating step S109, the binder is located in the same layer as the nonwoven fabric so as to maintain the three-dimensional structure inside the nonwoven fabric. Accordingly, the binder used in the present invention may be any binder that may maintain the three-dimensional structure inside the nonwoven fabric. The expression ‘maintain the three-dimensional structure inside the nonwoven fabric’ means that the binder, which is impregnated in the nonwoven fabric, may be distributed uniformly on the entire fiber yarn surface of the nonwoven fabric and maintain or further form irregular vent holes or microcavities, thereby maintaining the intrinsic internal three-dimensional structure within the nonwoven fabric.

Although a binder in the related arts may generally refer to a material used to bond or join two materials, the binder as used in the present invention may include a material impregnated in the nonwoven fabric formed of the heat-resistant fiber.

Various materials may be used as the binder impregnated into the nonwoven fabric. For example, a thermoplastic resin or a thermosetting resin may be suitably used as the binder material.

The thermoplastic resin such as a polyamide-based resin may have crystalline polar groups like the aramid fiber, which is a representative heat-resistant fiber. When a thermoplastic binder is impregnated into the nonwoven fabric formed of the thermoplastic heat-resistant fiber, a solid interfacial layer may be formed between the thermoplastic binder and the thermoplastic heat-resistant fiber due to face-to-face contact between their crystalline polar groups, thereby partially blocking or covering the vent holes of the nonwoven fabric. As a consequence, when a thermoplastic resin is used as the binder impregnated into the nonwoven fabric formed of the heat-resistant fiber, sound-absorbing performance may be reduced due to the partial blocking of the vent holes of the nonwoven fabric. At a glimpse, it may be thought that the sound-insulating performance would be improved if the vent holes are blocked. However, since noise is not eliminated inside the nonwoven fabric but is transmitted via other routes, improvement of the sound-absorbing performance may not be obtained if the thermoplastic binder is impregnated in the nonwoven fabric. In addition, when the thermoplastic binder is impregnated into a nonwoven fabric formed of the inorganic-based heat-resistant fiber, an adhesive additive may be added because of weak adhesive property between them.

In contrast, a thermosetting binder, as used herein, may have significantly different physical and chemical properties from those of the thermoplastic heat-resistant fiber. Accordingly, when a thermosetting binder is impregnated into the nonwoven fabric formed of the thermoplastic heat-resistant fiber, an interfacial layer is formed by edge-to-edge contact because of the different characteristics in phase. As a result, the vent holes or microcavities of the nonwoven fabric remain open. Therefore, when a thermosetting resin is used as the binder impregnated into the nonwoven fabric formed of the heat-resistant fiber, the three-dimensional structure inside the nonwoven fabric may be maintained. Accordingly, a thermosetting resin may be used as the binder in the present invention.

In addition, the thermosetting resin may be curable by light, heat or a curing agent and its shape may not change even under a high-temperature condition. Accordingly, in accordance with the present invention, the shape of the sound absorbing material can be maintained even under a high-temperature condition after molding by employing the heat-resistant fiber and the thermosetting binder under specific conditions. As a consequence, when the thermosetting binder resin is used as the binder impregnated into the nonwoven fabric, a desired shape may be molded during the curing of the resin and the shape can be maintained even under a high-temperature condition.

As described above, when the thermosetting resin is used as the binder impregnated into the nonwoven fabric formed of the heat-resistant fiber, the three-dimensional structure inside the nonwoven fabric may be maintained and molding into a desired shape may be obtained during the curing of the binder resin.

In particular, an epoxy resin may be used as the binder. The epoxy resin may be one of thermosetting resins and may be cured into a polymer martial having a three-dimensional network structure. Accordingly, since the epoxy resin forms a network structure and another vent holes when cured inside the nonwoven fabric, additional fine vent holes or microcavities may be formed inside the nonwoven fabric and the sound-absorbing performance may be further improved.

When the curing is carried out in the presence of a curing agent, a more complicated three-dimensional network structure may be formed, and thus, the sound-absorbing effect may be further improved. In detail, a three-dimensional network-structured polymer may be formed as the epoxide groups or hydroxyl groups of the epoxy resin react with the functional groups of the curing agent such as amine groups or carboxylic acid groups to form covalent crosslinkages. The curing agent may serve as a catalyst that catalyzes curing reaction and be involved in the reaction and linked to the chemical groups of the epoxy resin. Accordingly, the size and physical properties of the vent holes or microcavities may be controlled by selecting different curing agents.

The epoxy resin may be one or more epoxy resin selected from the group consisting of bisphenol A diglycidyl ether, bisphenol B diglycidyl ether, bisphenol AD diglycidyl ether, bisphenol F diglycidyl ether, bisphenol S diglycidyl ether, polyoxypropylene diglycidyl ether, bisphenol A diglycidyl ether polymer, phosphazene diglycidyl ether, bisphenol A novolac epoxy, phenol novolac epoxy resin and o-cresol novolac epoxy resin. The epoxy resin may have an epoxy equivalent of about 70-400. When the epoxy equivalent is less than the predetermined value, for example, less than about 70, intermolecular binding may be substantially reduced to form the three-dimensional network structure or the physical properties of the sound absorbing and insulating material may not be obtained sufficiently because of reduced adhesion with the heat-resistant fiber. In contrast, when the epoxy equivalent is greater than about the predetermined value, for example, greater than about 400, the sound-absorbing performance may not be sufficiently obtained because an excessively dense network structure is formed.

When the thermosetting resin is used as the binder in the present invention, a curing agent may be further included in the binder solution. As the curing agent, a compound having a functional group that may readily react with the functional groups of the thermosetting binder resin such as epoxide groups or hydroxyl groups may be used. For example, an aliphatic amine, an aromatic amine, an acid anhydride, urea, an amide, imidazole, and the like may be used as the curing agent. As specific examples of the curing agent, one or more selected from the group consisting of diethyltoluenediamine (DETDA), diaminodiphenylsulfone (DDS), boron trifluoride-monoethylamine (BF₃. MEA), diaminocyclohexane (DACH), methyltetrahydrophtalic anhydride (MTHPA), methyl-5-norbornene-2,3-dicarboxylic anhydride (NMA), dicyandiamide (Dicy), and 2-ethyl-4-methylimidazole may be used. Among those, an aliphatic amine- or amide-based curing agent may be used due to improved crosslinking ability and very superior chemical resistance and weather resistance. In particular, dicyandiamide (Dicy) may be used in consideration of crosslinking ability, flame retardancy, heat resistance, storage stability, processability, and the like. Since dicyandiamide (Dicy) has a high melting point above about 200° C., it may provide superior storage stability after being mixed with the epoxy resin and may ensure sufficient processing time for curing and molding.

As used herein, a catalyst may facilitate the curing of the thermosetting resin used as the binder may be used. The catalyst may be one or more selected from the group consisting of urea, dimethylurea, a tetraphenylborate salt of quaternary DBU, and quaternary phosphonium bromide. The catalyst may be contained in the binder-containing solution.

In addition, various additives, for example, a flame retardant, a heat resistance improver, a water repellent, and the like, may be used to provide additional functionalities to the sound absorbing and insulating material. The additive may be contained in the binder solution, and thus, no additional surficial material for providing functionalities to the sound absorbing and insulating material is necessary.

The flame retardant may be, but not limited to, a melamine, a phosphate, a metal hydroxide, and the like. For example, the flame retardant may be, but not limited to, one or more selected from the group consisting of melamine, melamine cyanurate, melamine polyphosphate, phosphazene, ammonium polyphosphate, and the like. In particular, the flame retardant may be, but not limited to, melamine, which enhances flame retardancy and heat resistance simultaneously.

The heat resistance improver may be, but not limited to, alumina, silica, talc, clay, glass powder, glass fiber, metal powder, and the like.

And, one or more fluorine-based water repellent may be used as the water repellent.

In addition, any additives commonly used in the related art may be selected depending on desired purposes.

The binder solution used in the binder impregnating step S109 contains, in addition to the binder resin, a curing agent, a catalyst, a commonly used additive and a solvent.

The binder, the curing agent, the catalyst and the additive contained in the binder solution are the same as described above. The solvent used to prepare the binder solution may be, but not limited to, one or more selected from the group consisting of a ketone, a carbonate, an acetate, a cellosolve, and the like. Specifically, the solvent may be one or more selected from the group consisting of acetone, methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK), dimethyl carbonate (DMC), ethyl acetate, butyl acetate, methyl cellosolve, ethyl cellosolve, and butyl cello solve.

In particular, the binder solution may include an amount of about 5-70 wt % of a binder and a solvent as the balance, based on the total weight of the binder solution. The binder solution used in the present invention may further contain other additives including a curing agent and a catalyst. For example, the binder solution may include an amount of about 5-70 wt % of a binder resin, an amount of about 0.1-10 wt % of a curing agent, an amount of about 0.01-5 wt % of a catalyst, an amount of about 1-40 wt % of an additive and a solvent as the balance, based on the total weight of the binder solution. In particular, the binder solution may include an amount of about 1-30 wt % of a binder, an amount of about 0.1-10 wt % of a curing agent, an amount of about 0.01-5 wt % of a catalyst, an amount of about 1-30 wt % of a flame retardant as an additive and an amount of about 40-95 wt % of a solvent, based on the total weight of the binder solution.

In the present invention, the degree of impregnation into the nonwoven fabric may be controlled with the concentration of the binder solution. For example, the binder solution may be prepared to have a solid content of an amount of about 1-60 wt %, or particularly of about 20-50 wt %, based on the total weight of the binder solution. When the binder solution includes the solid content less than about 1 wt %, suitable sound absorbing material may not be obtained because the content of the binder impregnated into the nonwoven fabric is small. In contrast, when the binder solution includes the solid content greater than about 60 wt %, the nonwoven fabric may become hard and may not serve as a sound absorbing and insulating material.

In addition, when the content of the curing agent contained in the binder solution is less that the predetermined amount, for example, less than about 0.01 wt %, molding to a desired shape may not be obtained because curing of the binder may not be completed. As a result, the effect of improving the mechanical strength of the sound absorbing and insulating material may not be achieved. When the content of the curing agent is greater than about the predetermined amount, for example, greater than about 10 wt %, the sound absorbing and insulating material may become hard and storage stability or the like may be unsatisfactory. Furthermore, when the content of the catalyst is less than the predetermined amount, for example, less than about 0.01 wt %, the effect for facilitating reaction may not be sufficiently provided. In contrast, when the content of the catalyst is greater than about the predetermined amount, for example, greater than about 5 wt %, storage stability and the like may be unsatisfactory. The additive may be one or more additive commonly used in the related art, which is selected from a flame retardant, a heat resistance improver, a water repellent, and the like The content of these additives may be adjusted adequately depending on the purpose of addition. When the amount of additives is smaller than the above-described range, the desired effect may not be achieved. And, when the amount of the additives is greater than the above-described range, it is undesirable in terms of economy and undesired side effects may be caused.

FIGS. 2A-2C show electron microscopic images showing exemplary three-dimensional structures inside of nonwoven fabrics before and after impregnation of a binder.

FIG. 2A is an electron microscopic image showing an exemplary internal structure of a nonwoven fabric before impregnation of a binder. It can be seen that heat-resistant fiber yarns cross each other to form irregular vent holes or microcavities. FIGS. 2B and 2B are electron microscopic images showing exemplary internal structures of the nonwoven fabric after impregnation of a binder. It can be seen that the binder may be finely and uniformly distributed and attached to the heat-resistant fiber yarns and that the content of the binder on the yarn surface may increase as the content of the binder increases.

As can be seen from the electron microscopic images of FIGS. 2A-2C, in the sound absorbing and insulating material of the present invention, the binder may be uniformly distributed on the surface of the heat-resistant fiber yarns constituting the nonwoven fabric.

The solvent recovering step S111 is a step to form a thermosetting felt. The thermosetting felt may include only the thermosetting binder resin present by evaporating the organic solvent from the binder-impregnated nonwoven fabric formed in the binder impregnating step S109. The solvent recovering step S111 may be performed using a drying oven at a temperature of about 70-200° C., or particularly of about 100-150° C., for about 1-10 minutes.

Through the solvent recovering step S111, harmful materials such as the organic solvent may be evaporated and be removed. The physical properties of the sound absorbing and insulating material may be controlled by controlling the binder content in the nonwoven fabric. The content of the binder contained in the dried nonwoven fabric is an important factor affecting the size, shape and distribution of the vent holes or microcavities inside the sound absorbing and insulating material, and the sound-absorbing performance and mechanical property of the sound absorbing and insulating material may be controlled therewith. In the present invention, the final content of the binder contained in the nonwoven fabric may be controlled to about 1-300 parts by weight, or particularly about 30-150 parts by weight, based on 100 parts by weight of the nonwoven fabric through the drying process. Through the drying process, the nonwoven fabric may be prepared into a thermosetting felt having a density of about 300-1500 g/m², or particularly of about 300-1000 g/m². The final content of the binder in the thermosetting felt may be controlled to about 50-800 g/m², or particularly about 100-500 g/m².

The present invention also provides a method for manufacturing a sound absorbing and insulating material, which further includes, after removing solvent, a molding step S121 of preparing a sound absorbing and insulating material by molding the dried nonwoven fabric at high temperature.

In particular, the method for manufacturing a heat-resistant sound absorbing and insulating material according to the present invention includes a beating and mixing step S101, a web forming step S103, a web stacking step S105, a needle punching step S107, a binder impregnating step S109, a solvent recovering step S111 and a molding step S121.

In the molding step S121, the dried nonwoven fabric obtained in the solvent recovering step S111 may be prepared into a sound absorbing and insulating material having a desired shape by molding at high temperature. The molding at such high temperature may also include or provide the curing of the thermosetting binder and may be performed at a temperature of about 150-300° C., or particularly of about 170-230° C.

The internal structure of the sound absorbing and insulating material manufactured according to the method of the present invention may be identified by electron microscopic images. The electron microscopic image reveals that, inside the sound absorbing and insulating material of the present invention, vent holes or microcavities having sizes of about 1-100 μm may be distributed regularly or irregularly with a spacing of about 0.1-500 μm.

FIG. 3 compares the heat-resistant sound absorbing and insulating material manufactured by the method of the present invention with a conventional aluminum heat protector.

The present invention also provides a method for reducing noise of a noise generating device, including: i) identifying the three-dimensional shape of a noise generating device; ii) manufacturing and molding a sound absorbing and insulating material so as to correspond partially or entirely to the three-dimensional shape of the device; and iii) bringing the sound absorbing and insulating material adjacent to the noise generating device.

The device may include any noise generating device including a motor, an engine, an exhaust system, and the like However, the device of the present invention is never limited to the motor, engine and exhaust system. The sound absorbing and insulating material may be manufactured to correspond partially or entirely to the three-dimensional shape of the device. Since the sound absorbing and insulating material of the present invention may be molded during the curing of the binder, the sound absorbing and insulating material of the present invention may be molded to correspond partially or entirely to the three-dimensional shape of the device.

As used herein, the expression “adjacent” may mean closely attaching the sound-absorbing material to the noise generating device, installing the sound absorbing and insulating material to be spaced apart from the noise generating device or molding the sound absorbing and insulating material as a part of the noise generating device. Further, the expression “adjacent” in the present invention may include installing the sound-absorbing material on a member (e.g., another sound absorbing and insulating material) connected to the noise generating device.

FIG. 4, FIGS. 5A-5B and FIGS. 6A-6B schematically show representative examples wherein an exemplary sound absorbing and insulating material of the present invention may be applied to a noise generating device of a vehicle.

FIG. 4 shows an exemplary heat-resistant sound absorbing and insulating material manufactured by an exemplary method of the present invention and a conventional aluminum heat protector, which are respectively installed to reduce radiated noise from an exhaust system.

FIGS. 5A-5B show examples wherein an exemplary sound absorbing and insulating material is molded and applied to a noise generating device of a vehicle. FIG. 5A shows an image of an exemplary sound absorbing and insulating material molded for use in a vehicle engine, and FIG. 5B shows an image of an exemplary sound absorbing and insulating material installed on a part of a vehicle engine.

FIGS. 6A-6B schematically show examples wherein an exemplary sound absorbing and insulating material may be applied to a noise generating device of a vehicle to be spaced apart from the noise generating device. FIG. 6A shows an image of an exemplary sound absorbing and insulating material molded for use in a lower part of a vehicle, and FIG. 6B shows an image of an exemplary sound absorbing and insulating material installed on a lower part of a vehicle.

As described above, since the sound absorbing and insulating material of the present invention, wherein a binder is impregnated into a nonwoven to maintain the three-dimensional shape inside thereof, has superior sound-absorbing performance, flame retardancy, heat resistance and heat-insulating property, it can exert its inherent sound absorbing and insulating effect when applied to a noise generating device maintained not only at normal temperatures but also at high temperatures of about 200° C. or greater without deformation of the molded product.

Examples

The present invention will be described in more detail through examples. However, the present invention is not limited by the examples.

Hereinafter, a method for manufacturing a substantially improved heat-resistant sound absorbing and insulating material according to various exemplary embodiments of the present invention and an effect of the substantially improved heat-resistant sound absorbing and insulating material will be described through examples.

Example 1 Preparation of Heat-Resistant Sound Absorbing and Insulating Material

1) Preparation of Nonwoven Fabric

A meta-aramid (m-aramid) fiber having 6 crimps/cm and a fineness of 2 denier and a length of 76 mm was beaten by air blowing and formed into a web of 30 g/m² through carding. The web was stacked by overlapping 10-fold on a conveyor belt operated at 5 m/min using a horizontal wrapper. A nonwoven fabric having a density of 300 g/m² and a thickness of 4 mm was prepared by performing single up needle punching, double down needle punching and then double up needle punching in a direction perpendicular to the surface of the stacked web.

2) Preparation of Thermosetting Binder Resin Solution

A thermosetting binder resin solution was prepared by mixing an epoxy resin consisting of a mixture of bisphenol A diglycidyl ether, polyoxypropylene diglycidyl ether and phosphazene diglycidyl ether with 10 wt % of a cyanoguanidine curing agent based on the epoxy resin, a 8 wt % of a bisdimethylurea compound based on the epoxy resin and 30 wt % of a melamine cyanurate flame retardant based on the epoxy resin.

3) Preparation of Thermosetting Felt

The thermosetting binder resin solution prepared in 2) was dispersed in a dimethyl carbonate (DMC) organic solvent such that the concentration of the thermosetting binder resin was 25 wt %. After immersing the nonwoven fabric prepared in 1) therein, a binder-impregnated nonwoven fabric having a density of 1,500 g/m² was formed by compressing at a pressure of 8 kgf/cm² using a mangle roller. The binder-impregnated nonwoven fabric was passed through a first drying oven set at 100° C., a second drying oven set at 120° C., a third drying oven set at 150° C. and a fourth drying oven set at 150° C. at a speed of 5 m/min, thereby removing 900 g/m² of the organic solvent such that 300 g/m² of the thermosetting binder resin remained. As a result, a thermosetting felt having a density of 600 g/m² was prepared.

Comparative Example 1 Preparation of Existing Aluminum Heat Protector

A heat protector was prepared from 1-mm thick aluminum, which is commonly used to insulate heat generated from an exhaust system, using a heat protector mold.

Comparative Example 2 Preparation of Sound Absorbing and Insulating Material Formed of Aramid Nonwoven Fabric

An aramid nonwoven fabric having a density of 300 g/m² and a thickness of 6 mm was prepared by needle punching in the same manner as described in Example 1, 1).

Comparative Example 3 Preparation of Sound Absorbing and Insulating Material Formed of Epoxy Resin-Coated Aramid Nonwoven Fabric

An aramid nonwoven fabric having a density of 300 g/m² and a thickness of 6 mm was prepared by needle punching in the same manner as described in Example 1, 1). Then, molding was performed after coating an epoxy resin on the surface of the nonwoven fabric such that the binder content was 50 parts by weight based on 100 parts by weight of the nonwoven fabric and drying at 150° C.

The coating solution contained 8 wt % of bisphenol A diglycidyl ether, 2 wt % of bisphenol A diglycidyl ether polymer, 0.2 wt % of dicyandiamide, 0.02 wt % of dimethylurea, 10 wt % of melamine cyanurate and 79.78 wt % of dimethyl carbonate, based on the total weight of the coating solution.

Comparative Example 4 Preparation of Sound Absorbing and Insulating Material Formed of Thermoplastic Resin-Impregnated Aramid Nonwoven Fabric

An aramid nonwoven fabric having a density of 300 g/m² and a thickness of 6 mm was prepared by needle punching in the same manner as described in Example 1, 1), immersed in a binder solution, dried and then molded.

A thermoplastic resin solution containing 10 wt % of polyethylene resin, 10 wt % of melamine cyanurate and 80 wt % of a dimethyl carbonate (DMC), based on the total weight of the thermoplastic resin solution, was used as the binder solution.

Comparative Example 5 Preparation of Sound Absorbing and Insulating Material Formed of Epoxy Resin-Impregnated PET Nonwoven Fabric

A polyethylene terephthalate (PET) nonwoven fabric having a density of 300 g/m² and a thickness of 6 mm was prepared was prepared by needle punching in the same manner as described in Example 1, 1), immersed in a binder solution, dried and then molded.

The PET nonwoven fabric of Preparation Example 5 showed thermal deformation due to the reaction heat generated during the epoxy curing process and showed complete thermal deformation during the drying and thermal molding processes. As a result, molding to a desired shape was impossible.

A 3-mm thick, substantially improved heat-resistant sound absorbing and insulating material test specimen was prepared by hot compressing the 600 g/m² thermosetting felt prepared in Example 1 at 200° C. for 200 seconds with a pressure of 100 kgf/cm².

The sound-absorbing rate of the substantially improved heat-resistant sound absorbing and insulating material test specimen was measured according to the ISO R 354, Alpha Cabin method. The average of the sound-absorbing rate measured for three specimens is given in Table 1.

TABLE 1 Frequency 1,000 Hz 2,000 Hz 3,150 Hz 5,000 Hz Sound-absorbing rate 0.07 0.18 0.37 0.66

The aluminum material showed a sound-absorbing rate of 0. In contrast, as shown in Table 1, the substantially improved heat-resistant sound absorbing and insulating material prepared according to the method for manufacturing a substantially improved heat-resistant sound absorbing and insulating material according to the present invention showed excellent effect of reducing noise inside a vehicle by reducing the noise radiated from an engine and an exhaust system when applied to a location closest to the engine and the exhaust system noise source.

While applying heat from a heat source maintained at 250° C. to the substantially improved heat-resistant sound absorbing and insulating material which was prepared by molding the thermosetting felt having a density of 600 g/m² prepared in Example 1 at 200° C. for 200 seconds with a pressure of 100 kgf/cm² using a heat protector mold and to the aluminum heat protector prepared in Comparative Example 1, temperature was measured on the opposite side. The result is shown in Table 2. In addition, to evaluate the performance of the substantially improved heat-resistant sound absorbing and insulating material prepared in Example 1, a 3rd gear W.O.T PG test was conducted on a diesel vehicle (U2 1.7). The result is shown in Table 3. Further, a result of measuring noise inside the vehicle under an idle neutral gear is shown in Table 4.

TABLE 2 Temperature measured on opposite side of sound absorbing and insulating material or aluminum heat protector (° C.) Heating time (sec) 0 100 200 300 400 500 600 Sound absorbing 0 98 107 112 113 114 115 and insulating material (Example 1) Aluminum heat 0 110 122 124 125 126 126 protector (Comparative Example 1)

From Table 2, it can be seen that the substantially improved heat-resistant sound absorbing and insulating material prepared according to the method for manufacturing a substantially improved heat-resistant sound absorbing and insulating material according to the present invention not only improves noise inside of a vehicle but also can protect nearby plastic and rubber parts by insulating heat, when applied instead of the aluminum heat protector which is commonly used to insulate heat.

TABLE 3 3rd gear W.O.T 2,000-4,000 rpm Product weight AI (%) average (g) Front seat Back seat Sound absorbing 170 81.4 80 and insulating material (Example 1) Aluminum heat 505 80 78 protector (Comparative Example 1)

TABLE 4 Neutral gear idle 400-6,300 Hz Product weight dB(A) rms (g) Front seat Back seat Sound absorbing 170 31.9 31.7 and insulating material (Example 1) Aluminum heat 505 32.9 32.7 protector (Comparative Example 1)

As can be seen from Table 3 and Table 4, when the substantially improved heat-resistant sound absorbing and insulating material prepared according to the method for manufacturing a substantially improved heat-resistant sound absorbing and insulating material according to the present invention was applied instead of the aluminum heat protector, booming noise was improved by 1.4-2% and the noise inside the vehicle was improved by 1 dB(A).

Test Examples Evaluation of Physical Properties of Sound Absorbing and Insulating Material

The physical properties of the sound absorbing and insulating materials were measured and compared as follows.

1. Evaluation of Heat Resistance

To evaluate heat resistance, the sound absorbing and insulating material was aged in an oven at 260° C. for 300 hours. After keeping at standard state (23±2° C., relative humidity of 50±5%) for at least 1 hour, appearance was inspected and tensile strength was measured. The appearance was visually inspected as to whether there was shrinkage, deformation, surface peeling, fluffing or cracking. The tensile strength was measured for five sheets of randomly selected dumbbell-type No. 1 test specimens at a speed of 200 mm/min under a standard condition.

2. Evaluation of Thermal Cycle

The durability of the sound absorbing and insulating material was evaluated by a thermal cycle test. The durability was determined after performing five cycles.

1) Condition of One Cycle

Room temperature→high temperature (150° C.×3 hr)→room temperature→low temperature (−30° C.×3 hr)→room temperature→humid condition (50° C.×95% RH).

2) Durability Evaluation Standard

After the thermal cycle test, the change in appearance was inspected. For example, surface damage, swelling, breaking and discoloring were inspected. If there was no change in appearance, it was evaluated as ‘no abnormality’.

3. Evaluation of Flame Retardancy

The flame retardancy of the sound absorbing and insulating material was measured according to the ISO 3795 flammability test.

4. Evaluation of Nonflammability

The nonflammability of the sound absorbing and insulating material was measured according to the UL94 vertical burn test.

5. Evaluation of Sound-Absorbing Property

The sound-absorbing performance of the sound absorbing and insulating material was measured according ISO354.

6. Evaluation of Air Permeability

1) Evaluation Method

The test specimen was mounted on a Frazier-type tester and the amount of air flowing through the test specimen vertically was measured. The area of the test specimen through which air passed was 5 cm² and the applied pressure was set to 125 pascal (Pa).

Test Example 1 Comparison of Properties of Sound Absorbing and Insulating Materials Depending on Heat-Resistant Fibers

In Test Example 1, the physical properties of sound absorbing and insulating materials prepared with different heat-resistant fiber yarns were compared. The sound absorbing and insulating materials were prepared according to the method of Example 1. For needle punching, yarns having a fineness of 2 denier and a length of 51 mm were used (see Table 5).

The results of measuring the properties of the sound absorbing and insulating materials prepared with different heat-resistant fibers are shown in Table 5 and Table 6.

TABLE 5 Yarn 1 Yarn 2 Yarn 3 Yarn 4 Yarn 5 Yarn 6 Yarn 7 Yarn Yarn material Aramid PPS PI PBI PBO Oxi-PAN PK Limiting oxygen  40  30  50  40  60  65  30 index Heat resistance 300 230 300 300 300 300 300 temperature (° C. × 1 hr) Heat Appearance No No No No No No No resistance abnor- abnor- abnor- abnor- abnor- abnor- abnor- mality mality mality mality mality mality mality Tensile strength 200 180 220 200 210 210 200 (Kgf/cm²) Thermal Appearance No No No No No No No cycle abnor- abnor- abnor- abnor- abnor- abnor- abnor- mality mality mality mality mality mality mality Flame retardancy Self- Self- Self- Self- Self- Self- Self- extin- extin- extin- extin- extin- extin- extin- guishing guishing guishing guishing guishing guishing guishing Nonflammability Nonflam- Nonflam- Nonflam- Nonflam- Nonflam- Nonflam- Nonflam- mable mable mable mable mable mable mable

TABLE 6 Sound-absorbing rate Frequency Yarn 6 (Hz) Yarn 1 (aramid) Yarn 2 (PPS) (oxi-PAN) Yarn 7 (PK) 400 0.08 0.05 0.08 0.05 500 0.10 0.06 0.09 0.06 630 0.16 0.09 0.13 0.08 800 0.23 0.15 0.22 0.19 1000 0.35 0.30 0.35 0.26 1250 0.44 0.39 0.45 0.37 1600 0.59 0.49 0.57 0.31 2000 0.70 0.66 0.68 0.48 2500 0.79 0.71 0.80 0.67 3150 0.83 0.80 0.85 0.78 4000 0.86 0.83 0.88 0.84 5000 0.99 0.95 0.92 0.83 6300 0.98 0.96 0.98 0.89 8000 0.99 0.95 0.89 0.95 10000 0.98 0.97 0.99 0.95

As seen from Table 5 and Table 6, all the sound absorbing and insulating materials prepared according to the present invention using heat-resistant fibers having a limiting oxygen index of 25% or greater and a heat resistance temperature of 150° C. or greater showed satisfactory heat resistance, durability, flame retardancy, nonflammability and sound-absorbing performance. Accordingly, it can be seen that any commonly used heat-resistant fiber may be used for the nonwoven fabric constituting the sound absorbing and insulating material of the present invention.

Test Example 2 Comparison of Properties of Sound Absorbing and Insulating Materials Depending on Density of Nonwoven Fabrics

In Test Example 2, the physical properties of the sound absorbing and insulating materials depending on the density of nonwoven fabrics were compared. The sound absorbing and insulating materials were prepared according to the method of Example 1. The density of the nonwoven fabrics was varied in the needle punching step. The sound-absorbing performance of the prepared sound absorbing and insulating materials is shown in FIG. 7.

As seen from FIG. 7, the sound-absorbing performance of the sound absorbing and insulating material was superior when the nonwoven fabric having a density of 600 g/m² was used as compared to when the nonwoven fabric having a density of 300 g/m² was used.

Test Example 3 Evaluation of Physical Properties of Sound Absorbing and Insulating Materials

In Test Example 3, the physical properties of the sound absorbing and insulating materials depending on the application type of the thermosetting binder in the nonwoven fabric when preparing the sound absorbing materials were compared.

That is to say, the sound-absorbing rate of the sound absorbing and insulating materials prepared by applying the thermosetting binder to the nonwoven fabric by impregnation (Example 1) or coating (Comparative Example 3) was measured. Table 7 shows the results of measuring the sound-absorbing rate for the sound absorbing and insulating material prepared from a nonwoven fabric (Comparative Example 2), the sound absorbing and insulating material prepared from a thermosetting binder-coated nonwoven fabric (Comparative Example 3) and the sound absorbing and insulating material prepared from a thermosetting binder-impregnated nonwoven fabric (Example 1).

TABLE 7 Sound-absorbing rate Example 1 Comparative (binder- Example 2 Comparative Example 3 impregnated (nonwoven (binder-coated nonwoven nonwoven Frequency (Hz) fabric) fabric) fabric) 400 0.01 0.02 0.08 500 0.03 0.03 0.10 630 0.12 0.05 0.16 800 0.16 0.08 0.23 1000 0.26 0.12 0.35 1250 0.32 0.15 0.44 1600 0.39 0.22 0.59 2000 0.48 0.29 0.70 2500 0.64 0.40 0.79 3150 0.63 0.57 0.83 4000 0.72 0.68 0.86 5000 0.80 0.77 0.99 6300 0.78 0.82 0.98 8000 0.89 0.98 0.99 10000 0.90 0.98 0.98

As seen from Table 7, the sound absorbing and insulating material of Example 1 according to the present invention exhibits superior sound-absorbing rate in all frequency ranges as compared to Comparative Example 2 wherein the nonwoven fabric not impregnated with a thermosetting binder was used as the sound absorbing and insulating material. In contrast, the sound absorbing and insulating material of Comparative Example 3 wherein the thermosetting binder resin-coated nonwoven fabric was used exhibits lower sound-absorbing rate in the frequency range of 400-5000 Hz as compared to Comparative Example 2.

Test Example 4 Evaluation of Heat-Insulating Performance of Sound Absorbing and Insulating Materials

In Test Example 4, the heat-insulating performance of the sound absorbing and insulating materials prepared in Example 1 (wherein the thermosetting resin-impregnated aramid nonwoven fabric was used), Comparative Example 2 (wherein the aramid nonwoven fabric was used) and Comparative Example 4 (wherein the thermoplastic resin-impregnated aramid nonwoven fabric was used). After applying heat of 1000° C. from one side of a 25-mm thick sound absorbing and insulating material sample for 5 minutes, temperature was measured on the opposite side of the sample.

The temperature measured on the opposite side of the sound absorbing and insulating material was 250° C. for Example 1 and 350° C. for Comparative Example 2. Accordingly, it can be seen that the sound absorbing and insulating material of the present invention wherein the thermosetting resin is impregnated has improved heat-insulating performance. In contrast, the sound absorbing and insulating material of Comparative Example 4 wherein a thermoplastic resin was impregnated was deformed as the thermoplastic resin was melted as soon as the heat of 1000° C. was applied.

These results show that the sound absorbing and insulating material of the present invention has very superior heat-insulating property.

Test Example 5 Comparison of Heat-Insulating Performance with Aluminum Heat-Insulating Plate

In Test Example 5, the heat-insulating performance of the sound absorbing and insulating material of Example 1 was compared with that of an aluminum heat-insulating plate. While applying the same heat from one side of the sound absorbing and insulating material and the heat-insulating plate at 250° C., the temperature at the opposite side was measured with time. The results are shown in FIG. 8.

As seen from FIG. 8, the sound absorbing and insulating material according to the present invention exhibited better heat-insulating performance by 11° C. or greater as compared to the aluminum heat-insulating plate.

Test Example 6 Comparison of Properties of Sound Absorbing and Insulating Materials Depending on Thermosetting Binder Resin Content

Sound absorbing and insulating materials were prepared as described in Example 1. The epoxy resin-impregnated aramid nonwoven fabric was dried to have different contents of the binder. The binder content was represented as parts by weight of the binder included in the sound absorbing and insulating material based on 100 parts by weight of the dried nonwoven fabric.

The results of comparing the mechanical properties and sound-absorbing rate of the sound absorbing and insulating materials of prepared with different binder contents are shown in Table 8 and Table 9.

TABLE 8 Physical properties of sound absorbing and insulating materials with different binder contents Binder content (parts by 0 10 50 100 200 weight) Air permeability 500 380 350 320 210 (mL/cm² · s) Tensile strength (kg/cm²) 40 60 200 240 310 Flammability Non- Non- Non- Non- Non- flam- flam- flam- flam- flam- mable mable mable mable mable

TABLE 9 Sound-absorbing rate of sound absorbing and insulating materials with different binder contents 0 part 100 parts 200 parts Frequency by 10 parts by 50 parts by by by (Hz) weight weight weight weight weight 400 0.01 0.01 0.08 0.06 0.02 500 0.03 0.04 0.10 0.09 0.04 630 0.12 0.14 0.16 0.15 0.09 800 0.16 0.17 0.23 0.25 0.11 1000 0.26 0.26 0.35 0.30 0.14 1250 0.32 0.34 0.44 0.42 0.17 1600 0.39 0.41 0.59 0.54 0.22 2000 0.48 0.55 0.70 0.58 0.35 2500 0.64 0.68 0.79 0.67 0.44 3150 0.63 0.69 0.83 0.72 0.52 4000 0.72 0.77 0.86 0.75 0.53 5000 0.80 0.83 0.99 0.79 0.57 6300 0.78 0.88 0.98 0.80 0.63 8000 0.89 0.91 0.99 0.90 0.70 10000 0.90 0.92 0.98 0.92 0.71

From Table 8 and Table 9, it can be seen that the impregnation of the binder in the nonwoven fabric provides improved sound-absorbing rate as compared to the nonwoven fabric wherein the binder is not impregnated. In addition, it can be seen that the sound-absorbing rate of the sound absorbing and insulating material may be controlled with the content of the binder.

Test Example 7 Comparison of Properties of Sound Absorbing and Insulating Materials Depending on Types of Binders

Sound absorbing and insulating materials wherein 50 parts by weight of a binder was impregnated based on 100 parts by weight of an aramid nonwoven fabric were prepared according to the method of Example 1. The resins described in Table 10 were used as the binder.

The results of comparing the mechanical properties and sound-absorbing rate of the sound absorbing and insulating materials prepared with different binders are shown in Table 10.

TABLE 10 Sound-absorbing rate of sound absorbing and insulating materials with different binders Binder resin Epoxy Phenol Urea Melamine Polyurethane Heat resistance 300 260 190 300 200 temperature (° C. × 1 hr) Tensile strength 200 165 180 180 170 (kg/cm²) Flame retardancy Self-extinguishing Self-extinguishing Self-extinguishing Self-extinguishing Self-extinguishing Flammability Nonflammable Nonflammable Nonflammable Nonflammable Nonflammable 

What is claimed is:
 1. A method for manufacturing a heat-resistant sound absorbing and insulating material, comprising: beating and mixing a fiber material comprising a heat-resistant fiber; forming a web from the beaten and mixed fiber material; stacking the formed web; forming a nonwoven fabric by needle punching as moving a needle up and down through the stacked web; forming a binder-impregnated nonwoven fabric by immersing the nonwoven fabric in a binder solution; and removing a solvent from the binder-impregnated nonwoven fabric.
 2. The method of claim 1, further comprising: shaping and molding the nonwoven fabric from which the solvent is removed into a desired shape.
 3. The method of claim 1, wherein the beating and mixing step comprises beating, mixing or beating and mixing a fiber material having a limiting oxygen index (LOI) of about 25% or greater and a heat resistance temperature of about 200° C. or greater.
 4. The method of claim 1, wherein the beating and mixing step comprises beating a fiber material having about 1-10 crimps/cm and having a diameter of about 1-33 μm and a length of about 20-100 mm or mixing one or more fiber material having about 1-10 crimps/cm and having a diameter of about 1-33 μm and a length of about 20-100 mm.
 5. The method of claim 3, wherein the fiber material comprises one or more selected from the group consisting of an aramid fiber, a polyphenylene sulfide (PPS) fiber, an oxidized polyacrylonitrile (oxi-PAN) fiber, a polyimide (PI) fiber, a polybenzimidazole (PBI) fiber, a polybenzoxazole (PBO) fiber, a polytetrafluoroethylene (PTFE) fiber, a polyketone (PK) fiber, a metallic fiber, a carbon fiber, a glass fiber, a basalt fiber, a silica fiber and a ceramic fiber.
 6. The method of claim 5, wherein the fiber material comprises one or more selected from the group consisting of a meta-aramid (m-aramid) fiber and a para-aramid (p-aramid) fiber.
 7. The method of claim 1, wherein the web forming step is performed by carding method.
 8. The method of claim 1, wherein the web stacking step is performed at a rate of 10 m/min or lower using a horizontal wrapper.
 9. The method of claim 1, wherein the needle punching step is performed by one or more selected from the group consisting of single down needle punching, single up needle punching, double down needle punching and double up needle punching.
 10. The method of claim 9, wherein the needle punching step comprises forming a nonwoven fabric with a needle stroke of about 30-350 times/m².
 11. The method of claim 1, wherein the nonwoven fabric formed in the needle punching step has a single layer thickness of about 3-20 mm and a density of about 100-2000 g/m².
 12. The method of claim 1, wherein the binder impregnating step comprises immersing the nonwoven fabric formed in the needle punching step in a binder solution wherein a thermosetting binder resin having a heat resistance temperature of about 200° C. or greater is dispersed in an organic solvent at a concentration of about 5-70 wt %.
 13. The method of claim 12, wherein the binder impregnating step further comprises compressing the binder-impregnated nonwoven fabric at a pressure of about 1-20 kgf/cm² to form a binder-impregnated nonwoven fabric having a density of about 1,000-3,000 g/m².
 14. The method of claim 12, wherein the binder impregnating step comprises impregnating an amount of about 20-80 parts by weight of a thermosetting binder resin in an amount of about 20-80 parts by weight of the nonwoven fabric.
 15. The method of claim 12, wherein the binder solution comprises an amount of about 5-70 wt % of a binder resin, an amount of about 0.1-10 wt % of a curing agent, an amount of about 0.01-5 wt % of a catalyst, an amount of about 1-40 wt % of an additive and a solvent as the balance, based on the total weight of the binder solution.
 16. The method of claim 15, wherein the binder solution comprises an amount of about 1-30 wt % of a binder resin, an amount of about 0.1-10 wt % of a curing agent, an amount of about 0.01-5 wt % of a catalyst, 1-30 wt % of a flame retardant and 40-95 wt % of a solvent, based on the total weight of the binder solution.
 17. The method of claim 12, wherein the thermosetting binder resin is an epoxy resin.
 18. The method of claim 17, wherein the epoxy resin is one or more selected from bisphenol A diglycidyl ether, bisphenol B diglycidyl ether, bisphenol AD diglycidyl ether, bisphenol F diglycidyl ether, bisphenol S diglycidyl ether, polyoxypropylene diglycidyl ether, bisphenol A diglycidyl ether polymer, phosphazene diglycidyl ether, bisphenol A novolac epoxy, phenol novolac epoxy resin, and o-cresol novolac epoxy resin.
 19. The method of claim 1, wherein the solvent recovering step comprises evaporating the organic solvent by drying in a drying oven at a temperature of about 70-200° C. for about 1-10 minutes.
 20. The method of claim 19, wherein the nonwoven fabric that has passed through the solvent recovering step comprises an amount of about 1-300 parts by weight of a binder based on 100 parts by weight of the nonwoven fabric.
 21. The method of claim 19, wherein the organic solvent is one or more selected from the group consisting of methyl ethyl ketone (MEK) and dimethyl carbonate (DMC).
 22. The method of claim 2, wherein the molding step is performed at about 150-300° C.
 23. The method of claim 1, which comprises: beating and mixing a fiber material having a limiting oxygen index (LOI) of about 25% or greater and a heat resistance temperature of about 200° C. or greater; forming the fiber material beaten and mixed in the beating and mixing step into a continuous web in the form of a thin sheet; forming a stacked web by overlapping and stacking the web formed in the web forming step with each other; forming a nonwoven fabric by binding the stacked web formed in the web stacking step with each other by moving a needle up and down through the stacked web; forming a binder-impregnated nonwoven fabric by immersing the nonwoven fabric formed in the needle punching step in a binder solution wherein a thermosetting binder resin having a heat resistance temperature of about 200° C. or greater is dispersed in an organic solvent; and forming a thermosetting felt for use as a sound absorbing and insulating material by removing the solvent from the binder-impregnated nonwoven fabric formed in the binder impregnating step such that only the thermosetting binder resin remains.
 24. The method of claim 23, which further comprises, after removing the solvent, shaping the nonwoven fabric into a desired shape by molding at a temperature of about 150-300° C.
 25. The method of claim 1, wherein the sound absorbing and insulating material has the binder distributed uniformly on the entire fiber yarn of the nonwoven fabric and has smaller-sized vent holes or microcavities formed as compared to before the impregnation of the binder.
 26. A method for reducing noise of a noise generating device, comprising: i) identifying the three-dimensional shape of a noise generating device; ii) manufacturing and molding a sound absorbing and insulating material by the method of claim 1 so as to correspond partially or entirely to the three-dimensional shape of the device; and iii) bringing the sound absorbing and insulating material adjacent to the noise generating device.
 27. The method of claim 26, wherein the device is a motor, an engine or an exhaust system.
 28. The method of claim 26, wherein said bringing the sound absorbing and insulating material adjacent to the noise generating device comprises closely attaching the sound absorbing and insulating material to the noise generating device, installing the sound absorbing and insulating material to be spaced apart from the noise generating device or molding the sound absorbing and insulating material as a part of the noise generating device.
 29. A vehicle part that comprises a heat-resistant sound absorbing and insulating material manufactured by a method of claim
 1. 